Gabor Szadovszky created PARQUET-1415:
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Summary: Improve logic when to write column indexes
Key: PARQUET-1415
URL: https://issues.apache.org/jira/browse/PARQUET-1415
Project: Parquet
Issue Type: Improvement
Reporter: Gabor Szadovszky
Assignee: Gabor Szadovszky
Currently, we always write column indexes. In case of the data is ordered
(ASCENDING or DESCENDING) the filtering would highly benefit from column
indexes. While, if the data is UNORDERED it is not obvious if ordering based on
column indexes would make sense. For example if the data is random then the
min/max values of the different pages might be close to each other so in most
cases filtering based on these values would not drop any of the pages. In the
other hand UNORDERED values does not mean that the values are random. It can
happen that the values are clustered or semi-ordered. We shall discover these
cases somehow before writing the column indexes and write only if the min/max
values for the pages do not overlap too much.
Another simple case if we have only one page. In this case writing column
indexes is useless.
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